Air-cooled gun



' AIR cooLED GN Filed March 6, 1945 66 1 6 /jZ/////////// /M PatentedSept. 16, 1947 UNITED STATES PATENT OFFICE (ci. ca -14.1)

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370O. G. 757) 25 Claims.

The invention described herein may be manul-factured and used by or forthe Goverment for governmental purposes without the payment to me of anyroyalty thereon.

My invention relates to improvements in automatic firearms, and itsgeneral object is to provide cooling means for such firearms wherebylonger periods of sustained effective automatic fire may be maintained,without damage to the firearm, and particularly the barrel thereof, thancan be obtained with automatic rearms employing the cooling means now inuse, or in which no cooling means are employed.

A further object of my invention is to provide means of this characterwhich may be utilized with the present standard automatic firearm, suchfor instance as the automatic firearm clisclosed in the patent to JohnM. Browning, No.

1,628,226 or other similar type firearms having a recoiling breechmechanism wherein a valving `action may be obtained in a port or orice,or a combination thereof, in the side Walls or casing or moving parts ofthe firearm by the action of such recoil mechanism in intermittentlyaligning such ports and orices and/or intermittently blocking -`same,depending on the specific 'type of recoil mechanism employed by thefirearm, by only slight alterations to the design of the presentfirearm, which alterations may be readily effected by any skilledmechanic with tools ordinarily available in any ordnance repair shop.

A still further object of my invention is to provide means of thischaracter wherein a uid cooling agent is employed and in which a streamor streams of the fluid are intermittently injected into the breech endof the bore of the barrel'during that portion of the period of automaticfire in which the bore is unblocked by the recoil mechanism and whilethe bore is free of either a loaded or empty cartridge case, theintermittent injections resulting from a valving action caused by therecoil mechanism and in which the supply of the cooling agent may becontrolled by movement of the trigger or other moving parts of thefirearm.

It is generally well recognized in the art that sustained automaticfiring or the firing of sustained bursts of shots in any automaticfirearm will heat the barrel of the arm to such a temperature that theeffectiveness of vthe re is greatly reduced or stopped entirely and thebarrel soon becomes unfit for further use. Excessively hot barrels causetrouble with ammunition resulting in cook ofi and also limits the use ofhigh explosive bullets in machine guns when the round -is left in thebarrel at the end of a burst of fire. Furthermore, the effectivefunctioning of the loading, extracting and ejecting mechanism isinterfered `with .by this overheated barrel condition and various'cooling devices, means ,and apparatus have been heretofore devised andproposed to cool -thebarrel or `.prevent overheating, but as `far asapplicant is aware, none of these have proved entirely satisfactory orare as simple as this design. Applicants means and apparatus providesfor the injection of a stream or streams of a cooling agent into thebreech end of the bore of the barrel of the firearm from an outsidesource after each shot is ired and, therefore, tends to keep the boreclear of gas .and minute particles created or caused by thefunctioningiof cartridges, or carried into the bore by same, in additionto preventing overheating of the barrel and consequent mal-functioning.vAnother advantage isithat the erosion caused by the burning gases isreduced. Cooling from the outside of thebarrel involves too much timelag in transmitting heat from the bore surface to the cooled `outersurface of the barrel.

'The cost of `altering the .design 0f firearms now Vin use to permitutilization of applicants invention will be negligible, whilefthe costof the additional equipment `required and the installation thereof willbe small compared with the benefits derived from the improvedperformance of the gun. While any suitable fluid may be employed as thecooling agent, .it is contemplated that compressed air will be thepreferreduid, which may Vbe supplied and replenished by .power derivedfrom the motors of airplanes, ships, armored cars, trucks, etc., Whenthefirearm `is positioned in .such vehicles or ships. Where no suitablepower ,source is available at the gun position for compressing air,suitable tanks or other containers of compressed air may :obviously beemployed, and when empty replaced 'by other tanks or containers, theempty tanks or containers being transported vto a source ,of supply forrefilling. Compressed 4air does not involve complications when operatingat sub-freezingtemperatures and `also is lighter than liquids.

While the specific structure shown and described in this application isadapted for use with 'the standard'Browning calibre `50 automaticfirearm now `in use, it will be obvious that same may be utilized inother automatic firearms, and may be employed 'to supplement the coolingof water cooled guns, if desired, wherein a water jacket surrounds allor a part ofthe barrel.

Slight `modiication of the structure shown herein may be necessary whenfirearms other than the Browning guns are used, as in the Browning gunreferred to, it is necessary to conduct the cooling agent through thecasing of the firearm as well as the barrel extension of same befo-reaccess can be had to the bore, and since the breech block isreciprocally mounted in the barrel extension and casing entry to thebore is blocked until the breech block recoils, and the orice in thebarrel extension through which the cooling agent passes is likewiseblocked by the breech block until one phase of the recoil movement iscompleted. rIhe barrel extension Vreferred to is, therefore, anintermediate structure between the casing and the entrance to the boreof the barrel, and in firearms where no barrel extension is provided andwhere the recoil mechanism operates directly against the side walls ofthe casing, the opening or openings in the casing or side walls may beinwardly and forwardly inclined to inject a stream'of fluid into thebore, as herein described in connection with the orifice in the barrelextension.

With the foregoing and other objects in view, as will hereinafter morefully appear and as will be more particularly pointed out in theappended claims, reference is now made to the accompanying drawingsforming a part of this application, in which:

Figure 1 is a fragmentary longitudinal crosssectional plan View of aportion of a machine gun embodying the invention, showing the cartridgestill in the barrel and the breech-bolt at its forwardmost position,

Figure 2 shows the portion of the gun illustrated in Figure l, thecartridge having been extracted from the barrel and the breech boltretracted, and

Figure 3 is a transverse cross-sectional View taken along the line 3 3of Figure 2.

' As illustrated in Figure 1, there is a machine gun casing or housing2, having side members 3 and 5, in which is slidably arranged a barrelextension 4 which is threadab-ly secured at its forward end 6 to therearward end 8 of a gun barrel I6. A cartridge case I2 is removablydisposed within the rearward end 8 of the bore I4 of the barrelv I inthe usual manner. The barrel extension 4 has two side members 1 and 9 inthe space between which is slidably arranged a f breech-bolt I6, shownin the illustration in its forward position with its forward 4end I8 incontact with the rearward end of the cartridge I2. A ring pin 28 iscarried by the bolt I8, for firing the cartridge I2.

When the cartridge is fired, the barrel I0, barrel extension 4 andbreech-bolt IB, being locked together, recoil rearwardly for a shortdistance, as is well known in the art pertaining to the Browning machineguns, and then the bolt I6 is unlocked from the barrel and barrelextension, and the bolt continues its rearward motion, carrying with itthe fired cartridge case, and thus exposing the rearward opening orbreech end 22 of the barrel bore I4, as indicated in Figure 2.

It is proposed as a feature of the present invention, to cool the barrelbore I4 by introduction of a cooling medium during the interval when thebreech bolt has been unlocked from the barrel and barrel extension andbefore the breechbolt has again returned to its forward position.

For this purpose a pair of oppositely disposed openings or ports 24 and26 are formed through side members 3 and 5 respectively of casing 2.

Hollow pipes or tubes 28 and 30 are connected at one end to openings 24and .26 respectively by means of any suitable tight coupling members 32and 34. The other ends of pipes 28 and 38 are connected to a source of acooling fluid such as an air compressor or air storage tank or container(not shown in the drawings), the pipes being connected together by a Tcoupling 38, A valve 49 of any usual design for quickly cutting off orturning on the air flow, is interposed in the air line between thecoupling 38 and the source of air 376. The valve 40 is of a type thatnormally remains closed until it is actuated, and then closes againautomatically when the actuating force ceases. Thus as illustrated, aplunger 42 is arranged inside the valve 48 so the bore 44 is normallyout of alignment with the bore 46. A trigger 48, pivotally mounted onpivot 50, is coupled to the outer end 52 of plunger 42 by rod 54. Aspring 58 disposed between the end of rearward gun housing 2 and aprojection 58 of the trigger 48, serves to keep the trigger 48 in closedposition. As the trigger 48 is depressed in the direction of the arrow59, the bore 44 in the plunger 42 is aligned with the bo-re 48, allowingthe cooling fluid to pass through the pipes 28 and Si), and the flowceases upon release of the trigger 48, which takes bore 44 out ofalignment with bore 45.

In the construction shown, the trigger 48 may be identical with theusual heavy machine gun trigger if desired, so that the cooling fluid isfree to pass up to and into the openings 24 and 26 while the gun triggeris depressed for ring the gun. In order to permitl the cooling uid toflow against and into the rearward or breech end of the bore i4 of thebarrel IIJy a pair of nozzle shaped openings or orices 68 and 62,inclined forwardly toward the bore I4 are formed through the sidemembers 'I and 9 respectively, of barrel extension 4. In order tominimize leakage of air through the space between the inner surfaces ofside members 3 and 5 of the housing, and side members 'I and 9 of thebarrel extension, two hollow cylindrical members 6I and 63 are slidablylocated within the couplings 32 and 34 respectively as indicated. Thesemembers have one end in constant contact with the outer abutting surfaceof side members I and 9 respectively, being pressed toward said abuttingsurfaces by coil springs 55 and 51 also located within couplings 32 and34 as shown. All piping, couplings and valves have inside diametersgreater than that of the orifices. As seen in Figure 1, the barrel eX-tension 4 and the bolt I6 and barrel Ill have not yet commenced theirrearward travel in recoilhence the cooling fluid in the openings 24 and26 cannot now against the rearward end of the bore I4. But when theiiring pin 2i) fires the cartridge I2, recoil begins, and the breechbolt and cartridge, the barrel extension and the barrel, move rearwardlyto a position indicated in Figure 2 at which the openings 68 and 62 arealigned, at one end with the openings 24 and 28, allowing the coolingmedium to flow into the openings 68 and B2. The barrel and barrelextension cease their rearward movement at this location, while thebreech bolt I6, carrying the cartridge case i4, continues its rearwardmotion, leaving vacant the space between the side members 'I and 9 ofthe barrel extension, and the cooling medium, now unrestrained, ows intothis space and against and into the rearward or breech end of the barrelbore I4, cooling same, and blowing out of it any particles of dust andunburned powder or residue and hot unburned gases remaining therein,which are important contributors to :overheating of 1the gun barrel.

Asthe bolt i6 :moves forvvardlyin counter-recoil fand is locked to thebarrel and :barrel extension, `the moving parts then `resume the,respective locations indicated `in Figure ,1, and the flow of coolingfluid against :the rear end of the barrel Vbore is cutoff.

The above cycle is repeated 'as long as-the gun `is ring, and serves tocool the gun barrel ,as indicated.

As shown in'Figure 3, the nozzles 60 and 62 may .fbe soangularlyfdisposed as to cause the cooling sfluid to ow -in thedirection of the arrows -64 and :66, thus also-giving it Va rotarymotion iconforming tothe cylindrical interior of the barrel bore,resulting in a better washing of the barrel land thermal `heat transferfrom the barrel to the air. This will greatly reduce the quantity -of.unburned gases coming back into tanks, particularly in a head wind.

While the invention is described above in specic terms, it is to beunderstood that various changes may be made in the size, shape,arrangement and materials without departing from the `spirit and scopeof the invention.

-I claim:

1. In an automatic firearm, a -breech casing lhaving `side walls `with aport formed therein and adapted to be connected to a supply of coolingagent, a barrel having a bore, a barrel extension on said `barrelsupported and guided forlongi- `tudinal movement in said casing, `saidbarrel-extension having therein an orice, said-orifice Vhav- -ingtheaXis thereof intersecting the bore -of the barrel and movingintoand-out of alignment with said port upon'the reciprocal longitudinalmovementfof said barrel `extension, whereby a cooling -agent isin-jected into the bore ofsaid barrel when said port vand saidorice arein aligned position.

.2. In an automatic firearm, a breech `casing having side walls with a:port formed'thereinvand 'adapted to be connected to a supply of coolingagent, a barrel having a bore, a barrel extension on said barrelsupported and guided for `longitudinal movement in said casing, saidbarrel -extension having therein anorifice, said orifice 'having theaxis thereof intersecting the bore of the barrel and moving into andoutof alignment with said port upon 4the reciprocal longitudinal .movementof said barrel extension, means conducting a cooling agent to said portand meanscontrolling Vthe flow of the cooling agent through said lastnamed means.

3. In an automatic rearm, a breech -casing having side walls with a porttherein andadapted vto be connected to a supply `of cooling agent, abarrel having a bore, a barrel `extension on said barrel supported andguided for longitudinal movement in rsaid casing, `said barrel extension`having therein `an orificey `said or-ice having the axis thereofintersecting the bore of -the bar-rel and moving into and out ofalignment with said port uponxthe reciprocal longitudinal `movement `ofsaid barrelextensicn, a conduit conducting `a .cooling agent to saidport, a valve inasaid conduit and lmeans connected to said valve foropening and closing the same.

4. In an automatic rearm, a-breech -casing having side walls with aplurality of ports therein, a barrel having a bore, `a barrel extensionon said barrel supported and guided for longitudi- 4nal movement in saidcasing, said barrel eXten- `sion having therein a plurality vof orificeslhaving the respective axes thereof intersecting the bore 'of ythebarrel, said orifices moving into and .out rif-:alignment with saidports rupon the reciprocal longitudinal movement of said barrelextension, wherebya cooling agent is intermittently injected into the`.bore y'of said barrel when said ports `and said orices are in-.alignedposition.

i5. 'Inzan automatic iireanm, the combination of abreech casing havingside walls, aibarrel having a bore, a barrel extension on `said barrelsupported and ,guided -forlongitudinal movement lin said casing, rmeansforminga port in said casing, -said barrel extension having an orifice"constructed :and Aarranged to intermittently align with said port, saidoriceihaving axis thereof'intersecting the-bore of `the barrel, acooling agent and means for injecting same into the bore of said barrelvwhen said `port and said orifice are in `aligned position.

6. In fan automatic rearm, the combination Aof abreech casing havingside walls, a barrel having a bore, a1barrel extension on said barrelsupported and guided for longitudinal movement in said casing, meansforming a port in said casing, said barrel extension :having an orificeformed there- Ain with its :axis intercepting'the breech entrance tothebore of-said barrel, said oricebeing `constructed and arranged ttointermittently 'align with said port during automatic fire of said fire-;arm, `a cooling agent -and means for injecting sameinto'said bore'through said orifice.

7. In an automatic firearm, the combination of a breech casing havingside walls, a barrel having a bore, `abarrel extension on said barrelsupported and :guided for'limited longitudinal reciprocalfmovement insaid casing, a breechlblock supported and vguided for a .greater limitedlongitudinal reciprocal move-ment than said 'barrel extension, meansforming a port in said casing, said barrel lextension having an orificeltherein with its .axisintercepting the `breech end of the bore-.of-said vbiarreLsaid orifice being constructed and arranged tointermittently align with `said port during the period in said movementVin which the barrel extension and breech bolt are in their respectiverearwardmost positions, a cooling agent and means forginjecting samethrough said .port and said -orice into the bore of said barrel.

8. -In an automatic 'rearrm `the `con'ibination of ya vbreech casinghaving side walls, abarrel .having a bore, a barrel extension on saidbarrel supportedand :guided for limited Ilongitudinal reciprocalmovement in said casing, -a breech block supported-and-guided for a.greater limited longitudinal reciprocal movement .than said barrelextension, means forming a' port in said casing, said `barrel extensionhaving `:an vorifice therein with its .axisxintersectingcthefbreecliendo the :bore ofaid barrel, saidorice'fbeing constructed .fandarrangedito .intermittently align with said portduring'the periodin'said movement in which the 4:barrel extension and breech `bolt are`in their respective .substantially vrearvvardmost positions,-aconduit-conducting a cooling-agent to said port, and a valveoperatively connected :to said firearm forcontrollingfthe now of ,theiagent to-said port.

9. In an automatic firearm, the combination of -a breech` casing havingsidewalls, a barrel having Aa'bore, a barrel extension onfthe barrelsupported and guided for limited longitudinal reciprocal movement insaid casing, a breech Yblock supported andfguided by said barrelextensionand said casing forfagreater limited longitudinal reciprocalmovement than said barrel, means forming-a plurality ofports in saidcasing, said barrel extension having a v'pluralityfof orifices thereinwith their axes intercepting lthe breech end of the bore of said barrel,said orifices being constructed and arranged to intermittently alignwith said ports during the period in said movement in which the b-arrelextension and breech bolt are substantially in their respectiverearwardmost positions, cooling agent and means conducting the same tosaid ports whereby the cooling agent is ejected through said ports andsaid orifices. into the bore of said barrel.

10. In. an automatic firearm, the combination of a breech casing havingside walls, a barrel having a bore, a barrel extension on said barrelsupported and guided for limited longitudinal reciprocal movement insaid casing, a breech block supported and guided by said barrelextension for a greater limited longitudinal reciprocal movement thansaid barrel extension, means forming a plurality of ports in. saidcasing, said 'barrel extension having a plurality of orifices thereinwith their axes intercepting the breech end of the bore of said barrel,said orifices being constructed and arranged to intermittently alignwith said ports during the period in said movement in which the barrelextension. and breech bolt are in substantially their respectiverearwardmost positions, a conduit conducting a cooling agent to saidports, and a valve operatively connected to said firearm for controllingthe flow of the agent to said ports.

1l. In an automatic iirearm, the combination of a breech casing havingside walls, a barrel having a bore, a barrel extension on said barrelsupported and guided for longitudinal movement in said casing, meansforming a plurality of ports in said casing, said barrel extensionhaving therein a plurality of orices constructed and arranged tointermittently align with said ports, said orifices having therespective axes thereof intersecting the bore of the barrel, a coolingagent and means conducting the same to said ports, Where- Iby thecooling agent is injected into the bore of said barrel when said portsand said oriiices are in aligned position.

l2. In an automatic firearm, the combination of a breech casing havingside walls, a barrel having a bore, a barrel extension on the barrelsupported and guided for longitudinal movement in said casing, with aplurality of ports in said casing, said barrel extension having aplurality of orifices therein with their axes intercepting the breechentrance to the bore of said barrel, said orifices being constructed andarranged to intermittently align with said ports during automatic iireof said firearm, a cooling agent and means for feeding same into saidports.

v13. In an automatic firearm, a breech casing having oppositely disposedside walls, a barrel having a bore, a barrel extension on the barrelsupported and guided for longitudinal, reciprocal movement in saidcasing between said walls, said Walls having a port therein, said barreleXtension having an orice therein with its axis intercepting the breechentrance of the bore of said barrel, said orifice being constructed andarranged to align with said port upon rearwardmost movement of saidbarrel extension.

14. In an automatic firearm, a trigger therein for initiating operationthereof, a breech casing having oppositely disposed side walls, a barreland a barrel extension supported and guided for longitudinal, reciprocalmovement in said casing between said walls, said walls having a porttherein, said barrel extension having an orifice thereln with its axisintercepting the breech entrance of the bore of said barrel, said oricebeing constructed and arranged to align with said port upon rearwardmostmovement of said barrel extension, a conduit connected to said port forconducting thereto a cooling agent and a valve in said conduitoperatively connected to the trigger Y of said firearm, whereby saidvalve is opened and closed by the movement of said trigger.

15. In an automatic rearm, a breech casing having oppositely disposedside walls, a barrel and barrel extension supported and guided forlongitudinal reciprocal movement in said casing between said walls, saidwalls having aport therein, said barrel extension having an orificetherein with its axis intercepting the breech entranceV of the bore ofsaid barrel, said orifice being constructed and arranged to align withsaid port upon rearwardmost movement of said barrel extension, theforward movement of said extension blocking said port, whereby a coolingagent is intermittently injected through said port and said orice intothe bore of said barrel.

16. In an automatic rearm, a trigger therein for initiating operationthereof, a breech casing having oppositely disposed side walls, a barreland barrel extension supported and guided for longitudinal reciprocalmovement in said casing between Said walls, said walls having a porttherein, said barrel extension having an oriiice therein with its axisintercepting the breech entrance of the bore of said barrel, said oricebeing constructed and arranged to align with said port upon rearwardmostmovement of said barrel extension, the forward movement 0f saidextension blocking said port, a cooling agent, a conduit for conductingsaid agent to said port, and a valve in said conduit operativelyconnected to the trigger of said firearm, whereby said valve is openedand closed by the movement of said trigger.

17. In an automatic firearm, the combination of a casing, a barrelhaving a barrel extension flanking the breech end of said barrel andsupported and guided for limited reciprocal longitudinalmovement in saidcasing, a breech block supported and guided for a greater reciprocal,longitudinal movement than said barrel extension, means forming aplurality of ports in said casing, said barrel extension having aplurality of orices therein having their axes intercepting the breechentrance to the bore of said barrel, said oriiices being Constructed andarranged to intermittently align with said ports upon reciprocalmovement of said barrel extension, whereby a cooling agent is injectedinto the breech end of the bore of said barrel when said breech blockand barrel extension are substantially at the limit of their respectiverearward movements.

18. In an automatic iirearm, the combination of a casing having sideWalls, a barrel having a barrel extension comprising spaced wallsconnected and extending rearwardly from the breech end of said barrelparallel with the casing side walls and supported and guided forreciprocal longitudinal movement therebetween, means forming ports insaid side walls and orices in said spaced walls with their axesintercepting the entrance to the breech end of the bore of said barrel,constructed and arranged whereby said ports and Said oricesintermittently align upon reciprocal movement of said barrel and barrelextension.

19. In an automatic iirearm, the combination of a casing having sidewalls, a barrel and barrel extension supported and guided for reciprocallongitudinal movement in said casing, and a breech block vsupported andguided for a greater reciprocal longitudinal movement than said barrelextension, said breech block blocking the entrance to the breech end ofthe bore of said barrel when in firing position and constructed andarranged to recoil for a limited distance with said barrel and barrelextension and to continue its recoil movement when the barre] and barreleX- tension reach their recoil limit thereby unblocking the bore of saidbarrel, with a port in said casing, said :barrel extension having anorifice constructed and arranged to align with said port when saidbarrel extension reaches its recoil limit.

20. In an automatic firearm, the combination of a casing having sidewalls, a barrel having a bore, a barrel extension on the barrelsupported and guided for reciprocal longitudinal movement in saidcasing, a breech block supported and guided for a greater reciprocallongitudinal movement than said barrel by said barrel extension and saidcasing, said breech block blocking the entrance to the breech end of thebore of said barrel when in firing position and constructed and arrangedto recoil for a limited distance with said barrel and barrel extensionand to continue its recoil movement when the barrel and barrel extensionreach their recoil limit, thereby unblocking the bore of said barrel,means forming a port in said casing, said barrel extension having anorifice constructed and arranged to align with said port when saidbarrel extension reaches its recoil limit7 means conducting a coolingagent to said port and manually operable means controlling the iiow ofthe agent to said port.

21. In an automatic iirearm, a casing having side walls, a barrel havinga bore, a barrel eX- tension on the barrel supported and guided forreciprocal movement in said casing, a breech block supported and guidedfor reciprocal movement by said barrel extension and said casing, saidbarrel, barrel extension and breech block being interconnected forsimultaneous travel together during the beginning and ending of areciprocal movement cycle, said barrel and barrel extension stoppingtheir movement and remaining stationary upon completion of the rearwardhalf of their movement cycle, while said breech block separates fromsaid barrel and continues its rearward movement to complete the rearwardhalf of its movement cycle, said breech block reengaging said barrel onits return movement, means forming a port in said side walls, saidbarrel extension having an orifice therein, said orice moving into andout of alignment with said port upon reciprocal movement cycle of saidbarrel extension, said breech block blocking said orifice duringengagement of said breech block with said barrel, and unblocking sameduring a substantial portion of that part of the movement cycle of saidbreech block in which the barrel is disengaged therefrom.

22. In an automatic iirearm, a casing having side walls, a barrel havinga bore, a barrel extension on said barrel supported and guided forreciprocal movement in said casing, and a breech block supported andguided for reciprocal movement by said barrel extension and said casing,said barrel, barrel extension and breech block being interconnected forsimultaneous travel together during the beginning and ending of areciprocal movement cycle, said barrel and barrel extension stoppingtheir movement and remaining stationary upon completion of the rearwardhalf of their movement cycle, while said breech block separates fromsaid barrel and continues its rearward movement to complete the rearwardhalf of its movement cycle, said breech lblock reengaging said barrel onits return movement, said side walls having a port therein, said barrelextension having therein an oriiice having the respective axes thereofintersecting the bore of the barrel, said orice moving into and out ofalignment with said port upon reciprocal movement cycle of said barrelextension, and said breech block blocking said orifice during engagementof said breech block with said barrel, and unblocking same during asubstantial portion of that part of the movement cycle of said breechblock in which the barrel is disengaged therefrom, whereby a coolingagent may be injected into the bore of Ysaidbarrel through said portandwsaid orifice when in aligned position and when said breech block hasunblocked said oriice.

23. In an automatic iirearm, a casing having side walls, a barrel andbarrel extension supported and guided for reciprocal movement in saidcasing, a breech block supported and guided for reciprocal movement bysaid barrel extension and said casing, said side walls having a porttherein, said barrel extension having an orice therein constructed andarranged to intermittently align with said port upon reciprocal movementof said barrel extension, whereby a valving action of said port iselected, and said breech block intermittently blocking and unblockingsaid orice, whereby a valving action on said orifice is effected.

24. In an automatic firearm, a casing having side walls, a barrel andbarrel extension supported and guided for reciprocal movement in saidcasing, a breech block supported and guided for reciprocal movement bysaid barrel extension and said casing, said side walls having aplurality of ports therein, said barrel extension having a plurality oforices therein, the reciprocal movement of said barrel extensionintermittently blocking said port and intermittently aligning saidorifices with said ports, whereby a cooling agent may be intermittentlyinjected through said ports and said orices, and said breech blockintermittently blocking said orices in its reciprocal movement, wherebya valving action of said orifices is eiected.

25. In an automatic firearm, a casing having side walls, a barrelsupported by said casing, a member slidably mounted between said sidewalls and actuated by :tiring pressure within said rearm, said side wallhaving a plurality of ports formed through ity said ports being valvedby the motion of said slidably mounted member to cause said ports to beopened for a predetermined interval of time during sliding movement ofsaid member, said ports being symmetrically arranged about said slidablymounted member whereby the side thrust on said slidably mounted memberby the iiuid pressure in said ports is substantially equalized.

BROOKS WALKER.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date .1,351,017 Blackmore Aug. 31,1920 543,567 Browning July 30, 1895

